Polymeric materials, including thermoplastics and thermosets, are used extensively in automotive vehicles and for other purposes. They are light and relatively easy to fashion into complex parts, and are therefore preferred instead of metals in many instances. However a problem with some polymers is salt stress (induced) corrosion cracking (SSCC), where a part under stress undergoes accelerated corrosion when under stress and in contact with inorganic salts. This often results in cracking and premature failure of the part.
Polyamides such as polyamide 6,6, polyamide 6, polyamide 6,10 and polyamide 6,12 have been made into and used as vehicular parts and other types of parts. While it has been reported that polyamides 6,10 and 6,12 are more resistant to SSCC (see for instance Japanese Patent 3271325B2), all of these polyamides are prone to SSCC in such uses, because for instance, various sections of vehicles and their components are sometimes exposed to salts, for example salts such as sodium chloride or calcium chloride used to melt snow and ice in colder climates. Corrosion of metallic parts such as fittings and frame components made from steel and various iron based alloys in contact with water and road salts can also lead to formation of salts. These salts, in turn, can attack the polyamide parts making them susceptible to SSCC. Thus polyamide compositions with better resistance to SSCC are desired.
U.S. Pat. No. 4,076,664 discloses a terpolyamide resin that has favorable resistance to zinc chloride.
European patent application 0272503 discloses a molding polyamide resin comprising poly(m-xylylenesebacamide) (PA MXD10) and a crystalline polyamide having a melting point about 20-30° C. higher than that of PA MXD10.
U.S. Pat. No. 6,841,651 discloses a polyamide resin including a diamine component comprising 70 mol % or more of m-xylylene diamine and a dicarboxylic acid component comprising 70 mol % or more of a C4-C20 aliphatic dicarboxylic acid.